Air-conditioners having a refrigerant or coolant heater are an equipment for heating a refrigerant by means of a refrigerant heater to utilize a heat produced thereby as a heat source in heating operation. FIG. 1 shows one example of such air-conditioners. In FIG. 1, at the time of the heating operation, a circulation circuit of refrigerant is formed by a compressor 1, a four port connection valve 2 (switching position of the solid line), an indoor heat exchanger 3, a valve 4, a refrigerant heater 5, and a check valve 6. On the other hand, at the time of the cooling operation, a circulation circuit of refrigerant is formed by the compressor 1, the four port connection valve 2 (switching position of the broken lines), an outdoor heat exchanger 7, a check valve 8, the indoor heat exchanger 3, and a check valve 9. Here, it is assumed that, at the time of the cooling operation, the valve 4 is closed. This invention is directed to a heating operation of an air-conditioner carried out by using the refrigerant heater 5 without use of the outdoor heat exchanger 7.
The refrigerant heater 5 used in the heating operation of an air-conditioner includes therein a fuel combustor or chamber supplied with fuel, e.g., gas through a control valve 10 to heat the refrigerant by heat produced by the combustor. The quantity of heat produced by the refrigerant heater 5 is controlled by adjusting the opening of the control valve 10 by means of a controller 20. Accordingly, the controller 20 adjusts the opening of the control valve 10 so that a room temperature becomes close to a set temperature thus to control a flow rate of the fuel.
Parts constituting the burning or combustion control system for heating refrigerant in such air-conditioners generally have large unevenness in their characteristics. In order to set minimum and maximum combustion quantities to respective predetermined values at the time when air-conditioners have been assembled, it is required to adjust individual control valves 10 at the area or place where the air-conditioners are assembled or installed. Generally, this adjustment includes a structural adjustment of the control valve 10 itself and an adjustment of the controller 20 combined with the control valve 10.
FIG. 2 shows the controller 20 in FIG. 1 in more detail. The controller 20 includes a combustion command signal generation unit 21 in which a plurality of steps of combustion command values corresponding to quantities of heat that the refrigerant heater 5 should produce are set, and a control valve controller 22 for controlling the opening of the control valve 10 on the basis of the combustion command values. At the combustion command signal generation unit 21, variable resistors 23 and 24 as the minimum combustion command adjustment means and the maximum combustion command adjustment means are provided, respectively.
The adjustment of control valve 10 and controller 20 is conventionally carried out as follows. First, the variable resistors 23 and 24 as the minimum combustion command adjustment means and the maximum combustion command adjustment means are provisionally set at intermediate positions, respectively. Thereafter, a minimum combustion command is caused to be sent from the control valve controller 22 to allow the opening of the control valve 10 to be in correspondence with a value corresponding to the minimum command value, thus to carry out a structural adjustment of the control valve 10 so that the combustion state of the refrigerant heater 5 results in the state corresponding to the minimum combustion command In this instance, since a structural fine adjustment of the control valve 10 is difficult, fine adjustment at the minimum combustion command point is carried out jointly by using adjustment of the variable resistor 23. Then, a maximum combustion command is caused to be sent from the control valve controller 22 to allow the opening of the control valve 10 to be in correspondence with a value corresponding to the maximum command value, thus to control the variable resistor 24 so that the combustion state of the refrigerant heater 5 results in a state corresponding to the maximum combustion command. The above-mentioned adjustments relating to the minimum value and the maximum value of a combustion quantity of the refrigerant heater 5 both rely upon delicate manual work by a skilled operator. However, since the combustion state of the refrigerant heater 5 varies to much degree by a small change of a quantity of fuel supplied as well, the above-mentioned adjustment work is generally difficult. Accordingly, in order to carry out the above-mentioned adjustment work, it takes a considerably long time. In addition, for the variable resistors 23 and 24, variable resistors of the multi-rotary type must be used in order to facilitate fine adjustment. This is disadvantageous from an economic point of view.